*{
    margin: 0;
    padding: 0;
    /*标准盒子*/
    /*box-sizing: border-box;*/
}
body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 20px;
    background-color: #f5f5f5;
}
li{
    list-style: none;
}
a {
    text-decoration: none;
}
.header {
    margin: 0;
    padding: 0;
    background-color: black;
    width: 100%;
    height: 50px;
}

.header .menu {
    display: flex;
    height: 100%;
    line-height: 50px;
    max-width: 600px;
    padding: 0 20px;
}
.header .menu li{
    height: 100%;
    color: white;
}
.header li:hover {
    background-color: #007bff;
    transition: color 0.5s;
}
.header .menu li a {
    font: bolder normal 16px Source Sans Pro;
    color: #fff;
    padding: 14px 15px;
}
.header .menu li p{
    font: bolder normal 16px Source Sans Pro;
    color: #fff;
    padding: 14px 15px;
}
.header .menu .用户设置的下拉菜单{
    display: none;
    position: absolute;
    background: black;
    /*border-radius: 5px;*/
}
.header .menu .用户设置的下拉菜单 li{
    padding: 0 0.5em;
    text-align: center;
}
.header .menu .用户设置:hover .用户设置的下拉菜单{
    display: block;
}

form {
    text-align: center;
    margin-bottom: 20px;
}

input[type="text"] {
    padding: 8px;
    font-size: 14px;
    border: 1px solid #ccc;
    border-radius: 4px;
    margin-right: 5px;
    width: 200px;
    box-sizing: border-box;
}

input[type="submit"] {
    padding: 8px 12px;
    font-size: 14px;
    border: none;
    border-radius: 4px;
    background-color: #007bff;
    color: #fff;
    cursor: pointer;
}
table tr:first-child{
    font-weight: bold;
    font-size: 20px;
    margin: 20px;
}
table tr td{
    text-align: center;
    align-items: center;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
}

table, th, td {
    border: 3px solid #ddd;
    text-align: center;
}

tr:nth-child(even) {
    background-color: #f9f9f9;
}

tr:hover {
    background-color: #f1f1f1;
}

table a {
    text-decoration: none;
    padding: 5px 10px;
    margin: 10px;
    display: inline-block;
    border: 1px solid #ccc;
    border-radius: 4px;
    background-color: #007bff;
    color: white;
}

table a:hover {
    background-color: #a29bf6;
    text-decoration: underline;
}
.简介{
    text-align: left;
}
.form{
    margin-top: 40px;
}
.add a{
    text-decoration: none;
    padding: 5px 10px;
    margin: 10px;
    /*display: inline-block;*/
    border: 1px solid #ccc;
    border-radius: 4px;
    background-color: #007bff;
    color: white;
}
.add a:hover {
    background-color: #a29bf6;
    text-decoration: underline;
}
.add p {
    color: red;
    text-align: center;
    font-size: 20px;
}